This invention relates generally to antennas used for space applications and, more particularly, to an oversized wide band, wide scan antenna which is stowed in a collapsed state and thereafter deployed when in orbit.
Extremely large scanning antennas for space applications and having limited scan requirements are well known. As the antenna is moved away from the Earth, the scan angles are reduced; however, the size of the antenna increases making the deployment and steering of very large antennas a formidable task. Such large scanning antennas typically use parabolic reflectors with clusters of feed elements at or near the focal point to scan the beam.
Accordingly, it is an object of the present invention to provide an improvement in wide band, wide scan antennas.
It is a further object of the invention to provide an improvement in wide band, wide scan antenna for space applications.
It is a further object of the invention to provide a light weight oversized wide-band, wide scan antenna for space applications which uses multiple reflectors as elements of a large aperture for a radar system deployed in space.
One aspect of the invention is directed to a deployable space borne antenna, comprising: a reflector support structure; a plurality of reflector cells mounted side by side in a concave spherical array in an interior portion of the support structure so as to form a radar aperture; each reflector cell includes a parabolic RF signal reflector and an RF feed assembly; each reflector having a flexible reflecting surface and a plurality of elongated edges defining a geometric shape, and including respective corner portions at the intersection of pairs of edges; respective rigid support members located at the corner portions of the reflector for stiffening the reflector and the elongated edges, and also for providing a support for the array of feed elements; a set of flexible support members extending between the rigid support members of each reflector cell and the respective array of feed elements for positioning the array above the RF signal reflector, and a mechanism located beneath each of the RF signal reflectors for pulling the respective flexible reflecting surface down to a substantially parabolic shape.
Another aspect of the invention is directed to a radar antenna system, comprising: a plurality of reflector cells mounted side by side in a concave spherical array; each reflector cell including a parabolic RF signal reflector and an RF feed assembly; wherein said RF feed assembly includes a plurality of feed elements arranged in a plane; and wherein said plurality of reflector cells operate in multiple groups of reflector cells and wherein each reflector cell generates a respective beam of radiation which combines to form a composite beam of radiation pointed in a predetermined direction.
Still another aspect of the invention is directed to a method of scanning a beam of radiation by a plurality of mutually adjacent parabolic reflector cells which are arranged in a concave array and which point to the center of a sphere, each respective cell having a feed assembly comprised of a set of feed elements arranged in a planar feed array, comprising the steps of: operating the plurality of reflector cells in a beam group of reflector cells selected for a predetermined pointing angle within a cone fixed by a center of the selected beam group; and, selecting and energizing a predetermined relatively small number of feed elements in comparison to the total number in said set of feed elements in the feed assembly of each reflector cell of said beam group which most closely points to a desired beam position.
Applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be noted, however, that the detailed description and specific example, while indicating the preferred embodiment of the invention is provided by way of illustration only, since alternations and modifications coming within the spirit and scope of the invention will become apparent of those skilled in the art from this detailed description.